skelett

Skelett is the internal framework that provides shape and support to an organism, protects vital organs, and enables movement through the action of muscles. It also serves as a reservoir for minerals and, in many animals, houses bone marrow where blood cells are produced. In some languages, including Swedish, the term skelett is used to refer to this internal structure; in English the equivalent word is skeleton.

In vertebrates, the endoskeleton is composed mainly of bone tissue and cartilage. The bones are organized into the axial skeleton, which includes the skull, spine, and rib cage, and the appendicular skeleton, which consists of the limbs and their girdles. Joints between bones allow movement, while protective structures such as the skull and rib cage shield the brain, heart, and lungs.

Bones grow and repair through ossification, with compact bone forming the dense outer layer and spongy bone creating a porous inner network. Long bones feature a central medullary cavity that contains marrow. Growth plates in children enable lengthening of the bones, and throughout life, bone is continually remodeled to maintain strength and mineral balance.

Other organisms exhibit different skeletal strategies. Some have external exoskeletons, such as many arthropods, while others rely on hydrostatic or other supportive systems. The term skeleton is sometimes used broadly to describe any rigid framework that supports and protects an organism.

In humans, bone density and structure vary with age and sex. Adequate intake of calcium and vitamin D, along with physical activity and sunlight, support healthy bones. Common issues include fractures and, with aging, osteoporosis.